King Gustav III of Sweden lost the war he started against Russia by talking too much. His archipelago fleet had just sunk or captured twenty-six Russian vessels in a few hours of close-range cannon fire off the Finnish town of Fredrikshamn — present-day Hamina — on 15 May 1790. The road into the harbor lay open. The town's fortifications were undermanned. With one decisive push the Swedes might have rolled up the entire Russian Gulf of Finland defense. Instead, when the Russian commander asked for an hour's respite to consider terms of surrender, Gustav granted it. In that hour Russian reinforcements arrived. By evening the Swedish fleet was withdrawing back to Svensksund, the chance gone. Two months later, at the Second Battle of Svensksund, Gustav would win the largest naval victory in Scandinavian history. But the missed chance at Fredrikshamn was the war in miniature: bold action, then sudden hesitation, then nothing.
Gustav III had picked the fight himself. By the late 1780s he needed a foreign victory to consolidate his shaky royal authority at home, and Russia under Catherine the Great seemed distracted by a Turkish war. In 1788 Sweden invaded Russian Finland. The campaign quickly bogged down. Russian ground forces held; Russian fleets bottled up the main Swedish navy; Swedish noble officers, never enthusiastic about a war they considered constitutionally illegal, mutinied at Anjala. By 1790 the war was in its third year and Gustav was running out of options. He decided to bet on the archipelago fleet — the special shallow-draft warships designed for the rocky, island-strewn waters of the Finnish coast, where deep-water battleships could not maneuver.
The Swedish coastal force at Fredrikshamn was an inventory of vessels that look like nothing in modern navies. There was one turuma and one pojama, two udemas — purpose-built archipelago frigates designed by the great Swedish naval architect Fredrik Henrik af Chapman. There was a xebec, eighteen oared galleys, forty gun sloops, thirty gun yawls, nine cannon longboats, and four mortar longboats. They could thread between islands at speeds that ocean fleets could not match, and they carried enough firepower to outshoot anything their size. The Russians had a smaller but similar collection under Pyotr Slizov, including their own turuma — the Sällan Värre, which the Russians had captured from the Swedes earlier in the war and which was about to change hands again.
The Swedes approached Fredrikshamn in the early morning of 15 May 1790. The Russians scrambled to meet them. What followed was a several-hour close-range gunnery duel in shallow water where neither side could withdraw far. The result was lopsided. Twenty-six Russian vessels were sunk or captured. The Sällan Värre was retaken and re-entered Swedish service, this time wearing its third national flag. The Russian heavy ships — which had the most firepower — could not maneuver into the shallows where most of the fighting happened, and several were captured intact. Smoke hung over the bay. The Russian survivors retreated under the guns of the shore batteries.
With the Russian fleet broken, Gustav sent his ships into the harbor and demanded the surrender of both the remaining vessels and the town fortifications. The Russian commander asked for an hour to consider. The polite request was a stall and the king should have known it. He granted the hour anyway. Couriers raced overland from nearby Russian garrisons. By the time the hour ended, the fort was reinforced and the defenders had set up positions to make a Swedish ground assault costly. Gustav tried anyway. The attacks broke against fresh defenders. By evening the Swedish fleet was withdrawing west toward Svensksund, having traded a strategic chance for a tactical victory that the Russians could replace within a year.
Two months later, on 9 July 1790, the Swedish archipelago fleet won the Second Battle of Svensksund — the largest Scandinavian naval engagement ever fought, with Russian losses of fifty-two ships and roughly 7,000 men. That victory was enough to bring Catherine to the negotiating table. The Treaty of Värälä in August 1790 ended the war with no territorial change. Sweden kept its Finnish provinces. Russia kept everything else. Gustav III went home claiming victory. Two years later he was assassinated at a masked ball by a Swedish noble who thought him a tyrant. Hamina — Fredrikshamn under its old Swedish name — kept its star-shaped Renaissance fortifications, which still survive in the town's compact octagonal street plan. The harbor where Slizov's fleet was wrecked is now a quiet Finnish port, with the lessons of 15 May 1790 written into the geometry of streets that Gustav once thought he could take in an afternoon.
Fredrikshamn — modern Hamina — sits at 60.52°N, 27.18°E on the Finnish Gulf coast about 145 kilometers east of Helsinki. The town's distinctive octagonal star-fort plan is unmistakable from low altitude, with concentric rings of streets radiating from the central square. Helsinki Vantaa (EFHK) is 130 kilometers west; St. Petersburg Pulkovo (ULLI) is 200 kilometers east. The Gulf of Finland archipelago — site of the battle and of Svensksund (modern Ruotsinsalmi/Kotka, 25 kilometers west) — is dotted with small islands. Best viewed at 2,000 to 4,000 feet AGL in clear weather, with the Russian-Finnish border 35 kilometers east and the Russian naval city of Vyborg 70 kilometers further on.